Imperial College London

Dr Craig Smalley

Faculty of EngineeringDepartment of Earth Science & Engineering

Visiting Professor







Royal School of MinesSouth Kensington Campus






BibTex format

author = {Smalley, PC and Dodd, TA and Stockden, IL and Råheim, A and Mearns, EW},
doi = {10.1144/GSL.SP.1995.086.01.05},
journal = {Geological Society Special Publication},
pages = {59--69},
title = {Compositional heterogeneities in oilfield formation waters: Identifying them, using them},
url = {},
volume = {86},
year = {1995}

RIS format (EndNote, RefMan)

AB - Two new techniques are now available for gaining information on formation water composition from core samples: core centrifugation, in which preserved core samples, complete with their preserved fluid content, are ultracentrifuged to extract the oil and water; and residual salt analysis (RSA), where salts are redissolved from unpreserved dry core and parameters such as 87Sr/86Sr are measured in the leachate. These methods are described and details given on the quality control measures that are crucial in order to avoid artefacts of core contamination by drilling fluids. Such methods have allowed formation-water compositional data to be obtained at the sub-metre scale, in some cases revealing significant small-scale variations (gradients and steps) in formation-water chemistry. Resistivity (related to salinity) variations are important for interpretation of water saturation from electrical resistivity logs, which in turn affects the estimate of the total amount of oil contained in the field. In the Machar chalk-reservoired oilfield, formation-water data derived by RSA and core centrifugation both indicate variations in salinity (TDS 140 000-220 000 ppm) that significantly affect resistivity. In some oilfields, assumption of a single resistivity value for the whole field could thus lead to errors in petroleum reserves estimation. Step changes in formation-water composition can be used as indicators of reservoir fluid compartmentalization, important for field development strategy. Examples are given of cases where RSA variations have been used to distinguish between laterally restricted and laterally extensive shales, both in the oil and water legs. Analysis of water compositional variation forms a valuable addition to the range of tools available for assessing reservoir compartmentalization during reservoir appraisal. This is because natural variations in fluid compositions provide quasi-dynamic data (i.e. how fluids have moved slowly during geological time), from whi
AU - Smalley,PC
AU - Dodd,TA
AU - Stockden,IL
AU - Råheim,A
AU - Mearns,EW
DO - 10.1144/GSL.SP.1995.086.01.05
EP - 69
PY - 1995///
SN - 0305-8719
SP - 59
TI - Compositional heterogeneities in oilfield formation waters: Identifying them, using them
T2 - Geological Society Special Publication
UR -
VL - 86
ER -